“Ode to a Nightingale” has an anxious and even unstable tone. This tone is defined in part by Keats’s choice to indent the lines of each stanza to varying degrees, creating a jagged visual aesthetic despite the poem’s fairly regular use of iambic pentameter. Echoing the visual instability of the line openings, the speaker’s shifting thoughts and emotions reflect an unsettled mental state. This mental instability first shows up in the speaker’s paradoxical claim that “a drowsy numbness pains / My sense” (lines 1–2). Despite being at once numb and in pain, the speaker goes on to insist that they don’t feel unhappy. To the contrary, they are in fact “too happy” (line 6), a phrase that suggests a heightened state we today might define as mania. The speaker longs to dampen the intensity of their mania through intoxication—first through alcohol, then later through poetry. Their thoughts about the immortality of poetry leads them to a slightly more balanced perspective on matters of life and death (lines 55–58):

                     Now more than ever seems it rich to die,
              To cease upon the midnight with no pain,
                     While thou art pouring forth thy soul abroad
                             In such an ecstasy!

But this balance falls apart in the final stanza. Unable to establish lasting mental stability, the speaker concludes in the same state of anxious heartache with which the poem began.